The present invention relates to the art of electric arc welding with a welder having a power supply of the switching type and more particularly to an electric arc welder of this type combined with a novel and unique controller to design the waveform.
Electric arc welding involves the movement of an electrode toward a workpiece while current is passed through the electrode and across an arc between the electrode and workpiece. Although some electric arc welders utilize a non-consumable electrode, most of the mass production arc welding involves an electrode which is consumed during the welding process whereby the electrode is melted by the arc and deposited on the workpiece. Thus, an arc welding process includes variable process characteristics, such as wire speed or electrode speed, gas composition, electrode diameter and workpiece metal. The actual electrical arc welding process at the production site takes into consideration these characteristics and involves a non-linear complex control system which determines the applicable metal transfer mode and the electrical parameters of the power supply performing the welding process. In order to achieve desirable results, a waveform is selected having several control parameters, which waveform is customized for the exact condition of each welding application. Thus, controlling arc welding has become an art which demands substantial knowledge and experience to select a waveform having several control parameters to produce an optimum welding process. A large number of controllers have been developed for use with electric arc welders that have real time current waveforms developed by welding engineers to optimize the welding process performed in the field. To accomplish this objective, a microprocessor based controller has been developed and is now used that allows an operator in the field to select one of many welding waveforms by merely using one of several overlays. This successful microprocessor based controller is illustrated in Blankenship U.S. Pat. No. 5,278,390 that is incorporated by reference herein. By using a known template for the controller, an operator selects a welding waveform having the desired control parameters especially developed for the selected weld process by a skilled welding engineer. This successful controller had a certain amount of adjustability in the field; however, such on-site adjustments were limited. Mass production use of arc welders has created a demand for the ability to conveniently adjust certain control parameters of the welding waveform in the field, especially when the welding process conditions are different than what is used in designing standard waveforms shipped with the welders (such as cable length, shielding gas and welding wire). Thus, there was a need for a controller to be used with an electric arc welder, where the controller can process a desired waveform that is adjusted interactively at the manufacturing site so the waveform is optimized for welding conditions and welding requirements for the job.
To fill this need, an electric arc welder was developed with a microprocessor based controller for the specific arc welder. This welder is shown in Hsu U.S. Pat. No. 6,002,104 incorporated by reference herein. The welder has a switching type power supply for creating a welding cycle, with a real time current waveform constituting several control parameters by rapidly switching a D.C. current in a controlled fashion by a pulse width modulator and it will be described with respect to such switching type power supply. This prior patented controller was used with various switching type power supplies normally used in electric arc welders; however, the Hsu patent shows a down chopper power supply for simplicity. In practice, an inverter type power supply having a waveform controlled by a pulse width modulator was controlled in accordance with the present invention. The microprocessor based controller included means for displaying a waveform generated on an electrically operated waveform screen, such as a CRT. In this manner, the operator at the production site viewed the actual waveform to be processed by the electric arc welder under the direction of the patented controller. Interactive means were employed for manually adjusting at least a portion of the waveform displayed on the waveform screen to generate a new waveform operating on the waveform screen and having the desired control parameters. Consequently, a prebuilt waveform was first displayed on the CRT, normally in a graph exhibiting current versus time. To change one of the control parameters, such as background current, peak current, current ramp, etc., a manual adjustment of the prebuilt waveform was performed manually and interactively on the waveform screen. In this manner, a new current waveform was exhibited on the waveform CRT screen. In accordance with somewhat standard practice, before the patented arc welder the pulse width modulator of the power supply was controlled in accordance with the newly created current waveform to cause the power supply itself to generate a welding cycle with the real time waveform corresponding to the new waveform on the waveform screen. The welder power supply executed the new control parameters exhibited as control parameters in the new waveform. In this manner, a desired waveform was exhibited and used by the electric arc welder. If there was a need to change a control parameter of the exhibited waveform, the waveform itself was modified visually by the operator on site and then employed for control of the electric arc welder. This interactive changing of the waveform, as it was visually displayed on a waveform screen, was novel to the welding field and was implemented by including a JAVA virtual machine with a welder control application program or an applet running within a browser in JAVA language. The JAVA control program was dedicated to the specific electric arc welder combined with the controller. Thus, the consumer product was an electric arc welder having a power supply with a microprocessor based controller that was driven by a program in JAVA language. This concept was accomplished by using a JAVA virtual machine as part of the on site controller. This new electric arc welding was interactively manipulated to create a waveform for controlling the actual real time waveform of the welding process. The controller performed its functions through real time adjustment of the pulse width modulator used in the switching power supply driving the welder.
In a welder using the patented technology of Hsu U.S. Pat. No. 6,002,104 the welder has a microprocessor with a JAVA virtual machine and controlled by at least one control application program in JAVA language. The program was dedicated to the particular welder being controlled. The microprocessor system included hardware with a first interface for an interactive display screen and a second interface for a manual data entry device, such as mouse or keyboard, that was used interactively to change the waveform on the display screen preparatory to the waveform being implemented on a digital communication link (such as ethernet or infrared) for outputting control parameters to the welder. The same communication channel was used to input operating parameters from the welder. In this manner, the electric welder was controlled by manual manipulation of the actual waveform to be used in the welding process preparatory to implementation of the welding process. As changes are required, certain control parameters were adjusted on the display screen to merely change the shape of the waveform being displayed. When the operating parameters from the welder were inputted to the microprocessor of the controller, a separate xe2x80x9cscopexe2x80x9d application program in JAVA language was selected and implemented by the controller. In this manner, the CRT of the controller was converted from a waveform editor to an oscilloscope display for reading parameters from the welder and for displaying these parameters as a soft oscilloscope on the face of the controller. The scope display used a window separate and distinct from the window used for editing the waveform. The screen of the controller was used to display either the waveform processed by the waveform editor application program or the oscilloscope plots processed by the scope application program. Both programs were processed by the JAVA virtual machine which was a part of the welder. The application programs were loaded into the virtual machine by a CD ROM that is loaded at the factory to program each of the welders preparatory to delivery. The physical media of distributing the JAVA object code or bytecode from the welding manufacturer to the customer used other forms, such as a floppy diskette, E-mail, web page and down loading by a modem. To change the operation program for the welders in the field, the patented welder periodically updated the control application program and/or the scope application program of the welders by a new CD ROM or by an Internet feed.
The patented controller of Hsu U.S. Pat. No. 6,002,104 displayed on its screen a waveform series of read out devices adjacent the waveform screen. A series of control parameters for the waveform were displayed adjacent the waveform screen, as read out values. The waveform was displayed on the waveform screen and contained a series of control parameters, some of which were recorded as read out values on the face of the controller adjacent the waveform screen. This total display is shown in FIG. 2 and is referred to as the graphic user interface or GUI. This display is used interactively to modify the waveform. The variable tables and waveform logic is provided by the memory stack as shown in FIG. 4. As an example of the display usage, the peak current of the waveform is displayed in an alpha numerical numbers on the face of the controller. As the waveform was modified interactively on the screen, the read out value was automatically changed accordingly. In addition, by adjusting one or more of the displayed control parameters at the read out device, the waveform itself was changed accordingly. The displayed control parameters, shown in the read out devices, had corresponding lock control parameter means for manually locking the display control parameters at preselected read out values. In this manner, the waveform was adjusted to change the value of a locked out control parameter. The prior art controller included a first override that was implemented to limit the value of one or more of the control parameters. In other words, if maximum current of the welder was at a set point, the control program processing a given waveform would prevent adjustment, either interactively or by a read out device, of the current to a level above the set maximum level. The same concept was used with a relational constraint wherein there is a fixed relationship of one control parameter to another control parameter. This fixed relationship was maintained. In this fashion, when one of the control parameters was adjusted, the other parameter is adjusted accordingly to maintain the set, fixed relationship. These are schemes utilized in the prior art patented welder to constrain the interactive manipulation of the waveform on the waveform screen or adjustment of the waveform through read out devices on the face of the controller. The JAVA virtual machine of the prior controller is provided with two or more application programs that are stand alone and can be selected by the operator who selects one or the other programs to be executed. The hardware of the controller includes a mouse or keyboard which latches onto certain points on the displayed waveform and allows the points to be moved or dragged in accordance with standard microprocessor operation. Consequently, there were graphically manipulating current waveforms for an arc welder in real time using JAVA technology. The welder monitors the actual waveform of the welder by analyzing operating parameters and using measurable electrical signals, such as arc current and voltage, derivative signals, such as impedance, power and energy, and process modes of operation. By using this concept, the operating signals or parameters from the welder itself were used to display and apply impedance of the arc and cable and instantaneous power of the arc and cable. Average current and voltage are sampled at a fixed rate and the welding time and the accumulated energy were also capable of being displayed in real time. If the optional scope program was employed, the output waveform created on the screen was analyzed and numerical data was displayed from various aspects of the displayed operating parameters. Other aspects of the actual operating condition of the welder were displayed and analyzed by using the scope program of the controller, not forming a part of the present invention.
In the prior art electric arc welder patented in Hsu U.S. Pat. No. 6,002,104, the processing logic was fixed and inflexible so that only certain types of waveforms pre-built into the program could be processed. For instance, a fixed wave shape template was selected for display and manipulation. See FIG. 3. The basic aspects of the template were fixed logic. Thus, the welder with a JAVA virtual machine could only select fixed templates for processing of specific current waveforms. There was no ability to select from a memory location certain data and display this as a waveform in a manner to change the behavior of the waveform template. In the prior art unit, the weld program compiled as object code or bytecodes was fixed to manipulate a fixed waveform logic of FIG. 4. If the waveform in FIG. 4 is changed, the JAVA source code must be changed to support the new waveform logic.
In electric arc welding, it has become well known to use a waveform generator to create an output waveform in an electric arc welder of the type driven by a high speed switching power supply, such as an inverter. In these welders, a welding engineer, or other skilled personnel, must load the values of the parameters and/or states into a state table or stack that is partitioned into work points, such as wire feed rates. By using a knob, a particular work point or wire feed speed is selected so that the state table controls the waveform generator by a commanded waveform with values and states that have been preprogrammed for a given work point. In Blankenship U.S. Pat. No. 2,578,390, this type of power supply is disclosed with a user interface for customizing the selected waveform to be used in the welder. An operator selects the desired waveform by manually or otherwise selecting the work point. Then, the waveform is displayed on a screen or CRT where it may be manually customized within certain internally provided constraints and relationships. To show this background information, Blankenship U.S. Pat. No. 5,278,390 and Hsu U.S. Pat. No. 6,002,104 are incorporated by reference herein.
In accordance with the present invention, a system and method is provided to duplicate a known recorded wave form from another power supply. For instance, if a welding facility desires to repeat the exact customized waveform from one STT welding machine to a second machine as shown in Blankenship U.S. Pat. No. 5,278,390, the present invention is used. In accordance with the invention, a desired target waveform is superimposed upon the same screen as the commanded waveform under development by the welding engineer. In practice this is done in two different colors. The welding engineer then drags and stretches the commanded waveform until it fits the superimposed target waveform. This is accomplished by a customizing procedure well known in the field and shown specifically in Hsu U.S. Pat. No. 6,002,104. Then, the welder is operated in accordance with the previously adopted waveform from another power supply. As an option, the actual waveform produced by the commanded, customized waveform is superimposed on the screen, whereby the difference between the actual waveform under development is matched to the target waveform to be duplicated. Thus, the target waveform is displayed with the commanded waveform. The actual waveform from the welder is sensed and transmitted back to the screen to be matched with the target waveform. This allows further customizing of the waveform to control and change any minor waveform differences. After this process has been done by the welding engineer, the new welder is loaded with the customized waveform as the commanded waveform control of the waveform generator. This commanded waveform is for a given work point, many of which will be available from the work point stack of the memory used in the controller of the welder. In practice, this method and system is automated by a software algorithm that manipulates the commanded waveform so that the differences between the actual waveform and the targeted waveform are minimized. This automatic customizing method and system is selected by an operator after the desired target waveform is displayed on the screen or is stored in memory in the controller. Consequently, in the automated implementation of the present invention, the display screen is not necessary.
The waveforms discussed herein are digitized and capable of being stored in the memory stack for each work point to be selected and displayed in the graphic user interface for customization. The digitized waveform to be copied is loaded into memory and then optically displayed on the CRT screen with the commanded waveform from the state table for a particular addressed work point.
Referring in more detail to the invention, a system is provided for creating an actual waveform at the output of an electric arc welder that is caused by a waveform generator. The welder has a display and customizing screen to design a commanded waveform for processing by the waveform generator. The system includes a program to display a target waveform on the screen. In practice, the waveforms are digitized and stored in memory. Another subroutine in the program is used to display the commanded waveform on the screen at the same time as the screen displays the target waveform. A computer terminal is used to manually customize the commanded waveform to generally match the target waveform. This system includes a pulse width modulator to cause the actual waveform to duplicate the commanded waveform directed to and controlling the operation of the waveform generator.
In accordance with another aspect of the invention, the actual waveform from the welder is digitized and displayed so that the actual waveform can be compared with the target waveform and customized so that the actual waveform matches the target waveform. Thus, the actual waveform is used to customize the commanded waveform for use in the waveform generator of the welder. In the invention, the waveforms are digitized and stored in memory for processing by the waveform editor or graphic user interface. In the preferred embodiment, the target waveform is an actual waveform of a remote welder so that the commanded waveform in the welder controlled by the invention matches either the commanded waveform of the remote welder or the actual waveform of the remote welder. It is more convenient to use the digitized commanded waveform of the remote welder instead of the actual waveform. This digitized data is easily obtainable from the controller of the remote welder.
In accordance with another aspect of the present invention, there is provided a method for creating an actual waveform at the output of an electric arc welder, which waveform is caused by a waveform generator. The welder is standard and includes a program for displaying a specific commanded waveform for use in controlling the waveform generator. This method comprises loading a target waveform into memory for processing by the program. A commanded waveform is stored in memory. The two stored digitized waveforms are then used to customize the commanded waveform to match the stored target waveform. Then, the customized commanded waveform is directed to the waveform generator to cause operation of the welder in a manner to produce a welding process having an actual waveform. This actual waveform matches the targeted waveform which is, in practice, a digitized commanded waveform from a remote welder.
The primary object of the present invention is the provision of a system and method for creating an actual waveform at the output of an electric arc welder, which waveform is caused by a standard waveform generator and wherein the actual waveform matches a desired target waveform from a remote welder.
Still a further object of the present invention is the provision of a system and method, as defined above, which system and method utilizes a standard graphic user interface to customize the commanded waveform to match the target waveform.
Still a further object of the present invention is the provision of a system and method, as defined above, which system and method can be easily implemented by a standard digital signal processor of an electric arc welder.
Yet a further object of the present invention is the provision of a system and method, as defined above, which system and method allows a welder to be operated in accordance with the desired waveform from a remotely located welder. Furthermore, this customizing capability can be trimmed by use of the actual waveform from the welder being controlled whereby the welder operates in accordance with the same waveform as the remote welder.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.